Impact cushioning device

ABSTRACT

An impact cushioning device including a hydraulic fluid cylinder, piston rod unit, the unit being equipped with an orifice tube having exponentially related slots for varying the flow of fluid resulting from impact, the fluid flow resulting from impact being used to compress a compressible fluid separated from the hydraulic fluid by means of an accumulator piston.

United States Patent Stembridge 1 Mar. 19, 1974 [5 1 IMPACT CUSHIONING DEVICE 3,139,159 6/1964 Lob 188/322 7 [76] Inventor: Harold E. Stembridge, 600 E. 3/68/68 2/1965 chorkey 188/787 Greenwood Ave, Mo Prospect, FOREIGN PATENTS OR APPLICATIONS Ill. 66056 518.063 11/1955 Canada 188/289 Filed: Oct. 1972 64,633 6/1955 France 188/289 [21] Appl. No.: 295,558 Primary Examiner-George E. A. Halvosa 152 us. (:1 188/285, 188/287, 188/315, [57] ABSTRACT 188/317, 188/322 An impact cushioning device including a hydraulic [51] Int. Cl F161 9/19 fl i ylinder, pi n rod i the unit ing q pp [58] Field of Search 188/284, 285, 287, 289, with an orifice tube having exponentially related slots 188/315, 316, 317, 318, 322; 16/51 for varying the flow of fluid resulting from impact, the

- fluid flow resulting from impact being used to com- [56] References Cited press a compressible fluid separated from the hydrau- UNITED STATES PATENTS lic fluid by means of an accumulator piston.

1,776,388 12/1930 Lomar 188/285 3 Claims, 2 Drawing Figures 3 47 4 a, 56 /3 l7 6, X 1 g I 31 24 2 /4 l I 32 5a" 3a 29 2a, 26 42 55 33 Z5 23 2 1 ,9 2o

IMPACT CUSHIONING DEVICE BACKGROUND AND SUMMARY OF. INVENTION This invention has to do with a decelerator mechanism, providing a uniform or constant rate of deceleration for a moving object. The impact cushioning device provides protection for products and moving and nonmoving parts of machines and equipment, and is useful as a safety device. Such installations as overhead cranes, conveyors, material handling processes, heavy steel doors, free fall elevators, shuttle cars, packaging machines and the like find utilization of the instant invention advantageous.

Although impact cushioning devices have been known in the past, these have suffered from a variety of drawbacks. The art has long been searching for a rugged, simple, quick acting, yet reliable device, and this is provided by the instant invention. According to the instant invention, a cylinder and piston rod unit is provided where the protruding end of the piston rod is adapted to receive impact. lnteriorly of the unit, a hydraulic fluid chamber is provided, and as the piston moves to reduce this space or chamber, fluid flow occurs which is selectively restricted, thereby providing a predetermined and constant resistance to load. The fluid which is displaced is employed to compress a compressible fluid which is separated from the hydraulic fluid in the unit by means of an accumulator ring or piston.

According to the invention, an impact cushioning device is provided which includes a hydraulic fluid cylinder, piston rod unit, and gaseous pressure charged ac cumulator, the unit being equipped with an orifice tube having exponentially located slots or orifices for the purpose of maintaining a constant pressure on the piston with a reducing velocity. The fluid displaced by the piston rod exerts a lower pressure on the accumulator ring piston compressing the gaseous precharge and thereby accommodating the displacement required by the absorption of the piston rod into the unit. This increase in pressure in the accumulator also serves to return the rod to the extended position when the load is removed.

Other objects and advantages of the invention may be seen in the details of the ensuing specification.

DETAILED DESCRIPTION The invention is described in conjunction with an illustrative embodiment in the accompanying drawing, in which:

FIG. 1 is a longitudinal sectional view through the cylinder and piston rod unit of the invention; and

FIG. 2 is an end elevational view of the unit of FIG. 1.

In the illustration given, and with particular reference to the central lower portion of FIG. 1, the numeral designates generally a cylinder which is closed at one end by means of an end closure 11, and at the other end by means of an end closure 12. Advantageously this is achieved through weldments as at 13 relative to the piston rod end closure 11, and at 14 relative to the other end closure 12. Mounted for reciprocation within the cylinder 10 is a piston generally designated 15. Secured to the piston 15 is a piston rod 16 which projects through the end closure 11 and which is equipped with a cap 17 which is adapted to receive the impact.

The portion of the cylinder between the piston 15 and the end closure 12 is designated 18 and constitutes a chamber for hydraulic fluid. Projecting into the chamber 18 from the end closure 12 are a pair of orifice tubes 19 and 20. The tubes 19 and 20 are concentrically related with the numeral 19, being applied to the inner of the tubes. Each tube is seen to be equipped with a plurality of circumferentially extending slots as at 21-25 relative to the outer tube 20, and as at 2630 relative to the inner tube 19. It will be noted that the slots 2125 are aligned with the slots 2630, respectively. Thus, upon an impact against the cap 17, the piston 15 moves to the right (in the showing in FIG. 1), and causes hydraulic fluid to flow through the various orifices 21-30.

It will be noted that the piston 15 is equipped with an axial bore, as at 31, into which the outer orifice tube 20 projects. Further, the rod 16 is equipped with an internal bore as at 32, which accommodates the projecting ends of the orifice tubes 19 and 20 upon movement of piston 15 to the right in FIG. 1. The piston rod 16 is equipped with a plurality of apertures 33 adjacent the piston 15 which permit hydraulic fluid to escape into the space 34. Hydraulic fluid being forced from the. chamber 18 by movement of piston 15 eventually flows through a passage or hole 35 in bearing 36, and exerts pressure against the accumulator ring-like piston 37. The space 38 behind the accumulator piston 37 is filled with a compressible gas, such as compressed air, which serves to absorb the displacement of the piston rod 16 as well as raising the internal pressure of the unit which will return the rod to the extended position when the load is removed.

SUMMARY OF OPERATION As a moving object comes into contact with the rod cap 17, the force of the kinetic or mechanical energy pushes the piston 15 towards the rear 12 of the cylinder 10. This increases the pressure of the hydraulic fluid in the chamber 18, forcing the fluid to seek a route of escape to an area of less pressure.

The path taken by the fluid is through the orifice slots 21-30 and into the axial portion of the cylinder 10, and further, toward the front end 11 of the cylinder 10. Most of the fluid exits through the left hand ends of the orifice tubes 19 and 20 and down the annulus between the outside diameter of the outer orifice tube 20 and the inside diameter of the piston rod bore 32. The fluid thereafter flows out of the openings 33 and into the area 34. A small amount of hydraulic fluid may also pass out of the orifice slots as at 25, 30 which by this time may have passed through the piston 15 and are now on the front side thereof.

As the piston rod 16 and piston 15 are depressed, there is more metal inside the cushion,and the pressurized fluid which is not compressible must find more room. The displaced fluid enters the bores 35 in the rear accumulator bearing 36 exerts pressure against the accumulator ring piston 37. The increased pressure of the fluid pushes the accumulator piston 37 forward,further compressing gas in the area 38 until the piston has reached the end of its travel.

During the process from the time the moving load makes contact with the rod cap 17 until the time the load has stopped and the rod 16 fully depressed, the kinetic or mechanical energy of the moving load has been largely changed to heat. The moving load contacts the rod 16 with full forces and begins to move the rod and attached piston inwardly of the cylinder 10. The hydraulic fluid contained in the chamber 18 seeks a path through the only available route (the orifice slot 21-30), but the oil cannot exit as fast as the impact load would dictate. Thus, the hydraulic fluid itself offers some resistance to movement of the piston 15, and consequently to the moving object. The resistance of the hydraulic fluid slows down the velocity of the moving object. The objective of the invention is to keep the resistance or pressure offered by the hydraulic fluid constant or uniform as both the velocity of the moving object decreases and the velocity of hydraulic fluid exiting chamber 18 decreases while the moving object is brought to a quick, gentle stop. To achieve this uniform resistance or pressure of hydraulic fluid, successive orifice slots as at 29-24, 28-23, etc. are closed to the oil escaping from the area 18 as they enter the piston 15 and pass through it.

The orifice slots 21-30 are unevenly spaced and mathematically related to the decreasing velocity of the moving object in that the spacing of the adjacent orifices in a given tube are exponentially related or located in order to maintain constant pressure with a decreasing velocity.

. VARIATION IN RESISTANCE To accommodate various weights and velocities, the size of the combined, aligned orifice slots (as at 25-30, 24-29, etc.) can be changed through the rotation of the external knob 39 (see the extreme right hand center portion of FIG. 1). The rotation of the knob 39 results in a corresponding rotation of the inner orifice tube 19 relative to the outer orifice tube so as to enlarge or lower the passage area in the aligned slots. The orifice slots on both the inner and outer orifice tubes are sharp-edged so as to achieve a constant pressure drop.

For the purpose of permitting rapid adjustability of the resistance to flow of hydraulic fluid, as by changing the orifice open area, the inner orifice tube 19 projects further to the right (as at 40) than does the outer orifice tube 20. Fixed to the projecting portion 40 of the inner orifice tube 19 is a flange 41 which is further equipped with an integral stem as at 42. It is to the stem 42 that the knob 39 is affixed. The outer orifice tube 20 is also equipped with a flange as at 43 which is stationary within a bore 44 of the end closure 12.

ACCUMULATOR DETAILS Within the cylinder 10 I provide a pair of bearings 45 and 46 for the piston rod 16. More particularly, an outer cylindrical wall 47 is provided for the accumulator piston 37. This sleeve or lining within the cylinder 10 connects with and anchors the two circular bearings 45 and 46. I also provide an inner cylinder wall 48 for the accumulator ring piston 37 the inner cylinder wall 48 like the outer cylinder wall 47 for the accumulator extending between the bearings 45 and 46. To provide compressed air or gas for the space 38 ahead of the accumulator piston 37, a conduit 49 is provided in the bearing 46. This conduit is adapted to be connected to an air valve (not shown) so as to put a precharge of compressed air or gas into the accumulator.

HYDRAULIC FLUID RECHARGE Inasmuch as hydraulic flid is dissipated, albeit in small quantities, from time to time (particularly through rod wipage), I provide means for augmenting the supply of hydraulic fluid. Referring to FIG. 2, the numeral 50 designates a quick connect fitting which allows hydraulic fluid to be added to the unit while the same is in operation. The fitting 50 is arranged to be in communication with the bore 51 in the end closure 11. The bore 51 is communicated via a passage 52 to the space 53 between the end closure 11 and the bearing 46. The bearings 46 and 45 are grooved as at 54, which permits added oil to flow into the small annular space 55 between the piston rod 16 and the accumulator cyb inder inner wall 48. The added fluid ultimately reaches the space 34, and from there passes into the chamber 18 by virtue of passing through a check valve generally designated 56. This check valve is also unique in that it consists of a drilled hole smaller than the ball, counterbored slightly larger than the ball, and the ball is effectively retained by a pin, as at 56a, pressed, into a cross-drilled hole which intersects the larger portion of the passage.

In summary, to add hydraulic fluid to the unit which may have been lost because of the rod wipage, a suitable gun (not shown) is attached to the quick connect check valve type fitting 50 and fluid is pumped into the unit. Fluid passages through the passage 52 into the clearance between the rear of the packing gland 57 provided as part of the end closure 11 and the front of the accumulator (defined by the front bearing 46). Thereafter it passes through the groove 54 into the annulus or clearance 55 between the rod 16 and the accumulator cylinder wall 48. Thereafter the oil flows through further grooves 58 (akin to the grooves 54), but these are in the rear bearing 45. Grooves 54 and 58 are semicircular slots or grooves completely through bearings 45 and 46, there being no contact betwen the rod and bearing at these points, permiting free passage of oil. The fluid thereafter flows into the space 34 which is advantageously enlarged by slots 59 provided in the front face of the piston 15. Optimally, three U- shaped slots 59 are provided which are aligned with the openings 33 in the piston rod 16. Thereafter, fluid flows through the check valve arrangement 56 into the chamber 18 as well as through the orifice tubes 19 and 20 and out the orifices 21-30.

A second radial bore (not shown) but like the one designated 51 for the filling of oil, is provided to communicate with the space 53. This in turn is coupled to a relief valve 60 (see FIG. 2). Thus, an over fill is discharged out the relief valve. Still referring to FIG. 2, the numeral 61 refers to a plurality of holes in the front flange portion of the end closure 11 which permit the unit to be attached to a supporting structure (not shown). Here it will be appreciated that the internal pressurized accumulator positively separates air and oil and allows mounting of the unit in any position, including rod down, in which case compressible gas must be excluded from chamber 18, thereby accommodating the unit to a variety of installations.

I also provide indicia as at 62 (see the left central portion of FIG. l) in the form of an integral black stripe on the rod 16 so as to indicate the need for fluid addition. When the rod, after the impact load is removed, returns to its extended position, the indicia 62 should be visible. If not, it is a ready and simple indication for the need of additional fluid.

It will be noted that the simplicity and reliability of operation is enhanced by the mounting of the orifice tubes along the axis of the cylinder unit and with the provision for the projection of the orifice tubes 19 and 20 into the piston rod bore 32. Further,through the use of a single cylinder 10, rapid heat dissipation is achieved.

While in the foregoing specification a detailed description of an embodiment of the invention has been set down for the purpose of illustration, many variations in the details herein given may be made by those skilled in the art without departing from the spirit and scope of the invention.

1 claim:

1. An impact cushioning device or linear decelerator comprising a cylinder having a piston reciprocally mounted therein, said cylinder being equipped with closures at the ends thereof, a rod connected at one end thereof to said piston and projecting out of one of said end closures and adapted to receive impacts, said rod at its piston end having an axially extending bore and said piston having a bore therethrough communicating with the rod bore, a pair of concentrically related orifice tubes mounted on the other of said end closures and projecting into the bores of said piston and rod, each of said orifice tubes being equipped with orifice means adapted to be brought into various degrees of alignment thereby altering the flow area to change the resistance of hydraulic fluid flow through said oriflce means upon movement of said piston toward said other end closure, means operably associated with the other end closure for changing the alignment of said orifice means, an accumulator ring piston in said cylinder between said piston and said one end closure and spaced therefrom, said rod being equipped with an aperture communicating said rod bore with the space between said piston and said accumulator ring piston whereby hydraulic fluid flowing in said bores upon piston movement toward said other end closure is adapted to exert pressure on said accumulator ring piston, and a compressible fluid in the space between said accumulator piston and said one end closure, said cylinder being equipped with a pair of spaced-apart bearings for said rod, said accumulator ring piston being interposed between said rod bearings, the bearing between said piston and accumulator ring piston being equipped with a through bore to deliver hydraulic fluid pressure to said accumulator ring piston, the bearing between said accumulator ring piston and said one end closure being equipped with a passage for introducing compressible fluid into the space between said accumulator ring piston and the last-mentioned bearing.

2. The structure of claim 1 in which said accumulator ring piston is an annulus having an axial bore, a cylinder wall for said annulus bore being supported by said bearings, said cylinder wall being in close proximity but spaced from said rod to provide a passage for addition of hydraulic fluid, a filling conduit in said one end closure for delivering replacement hydraulic fluid to said passage, and check valve means in said piston whereby hydraulic fluid can be added to the space between said piston and said other end closure.

3. The structure of claim 2 in which said rod is equipped with indicia for indicating when additional hydraulic fluid is required in said space. 

1. An impact cushioning device or linear decelerator comprising a cylinder having a piston reciprocally mounted therein, said cylinder being equipped with closures at the ends thereof, a rod connected at one end thereof to said piston and projecting out of one of said end closures and adapted to receive impacts, said rod at its piston end having an axially extending bore and said piston having a bore therethrough communicating with the rod bore, a pair of concentrically related orifice tubes mounted on the other of said end closures and projecting into the bores of said piston and rod, each of said orifice tubes being equipped with orifice means adapted to be brought into various degrees of alignment thereby altering the flow area to change the resistance of hydraulic fluid flow through said orifice means upon movement of said piston toward said other end closure, means operably associated with the other end closure for changing the alignment of said orifice means, an accumulator ring piSton in said cylinder between said piston and said one end closure and spaced therefrom, said rod being equipped with an aperture communicating said rod bore with the space between said piston and said accumulator ring piston whereby hydraulic fluid flowing in said bores upon piston movement toward said other end closure is adapted to exert pressure on said accumulator ring piston, and a compressible fluid in the space between said accumulator piston and said one end closure, said cylinder being equipped with a pair of spaced-apart bearings for said rod, said accumulator ring piston being interposed between said rod bearings, the bearing between said piston and accumulator ring piston being equipped with a through bore to deliver hydraulic fluid pressure to said accumulator ring piston, the bearing between said accumulator ring piston and said one end closure being equipped with a passage for introducing compressible fluid into the space between said accumulator ring piston and the last-mentioned bearing.
 2. The structure of claim 1 in which said accumulator ring piston is an annulus having an axial bore, a cylinder wall for said annulus bore being supported by said bearings, said cylinder wall being in close proximity but spaced from said rod to provide a passage for addition of hydraulic fluid, a filling conduit in said one end closure for delivering replacement hydraulic fluid to said passage, and check valve means in said piston whereby hydraulic fluid can be added to the space between said piston and said other end closure.
 3. The structure of claim 2 in which said rod is equipped with indicia for indicating when additional hydraulic fluid is required in said space. 